For example, Patent Literature 1 describes a two-stage pressure buildup refrigeration cycle apparatus. In Patent Literature 1, in a cycle using a plurality of compressors, refrigerant discharge capacity of a high-pressure side compression mechanism and refrigeration discharge capacity of a low-pressure side compression mechanism can be controlled independently of each other. The refrigeration discharge capacity of the low-pressure side compression mechanism is determined based on an atmospheric temperature, an air temperature, and a set temperature. The refrigerant discharge capacity of the high-pressure side compression mechanism is determined so that an effective capacity ratio is in a range of 1 to 3, based on the determined refrigerant discharge capacity of the low-pressure side compression mechanism. In this way, a COP of the two-stage pressure buildup refrigeration cycle apparatus is improved with a simple configuration and control.